Distinct roles for prominin-1 and photoreceptor cadherin in outer segment disc morphogenesis in CRISPR-altered X. laevis.

Mutations in prominin-1 (prom1) and photoreceptor cadherin (cdhr1) are associated with inherited retinal degenerative disorders but their functions remain unknown. Here, we used CRISPR-Cas9 to generate prom1-null, cdhr1-null, and prom1 plus cdhr1 double-null Xenopuslaevis and then documented the effects of these mutations on photoreceptor structure and function. Prom1-null mutations resulted in severely dysmorphic photoreceptors comprising overgrown and disorganized disc membranes. Cone outer segments were more severely affected than rods and had an impaired electroretinogram response. Cdhr1-null photoreceptors did not appear grossly dysmorphic, but ultrastructural analysis revealed that some disc membranes were overgrown or oriented vertically within the plasma membrane. Double-null mutants did not differ significantly from prom1-null mutants. Our results indicate that neither prom1 nor cdhr1 are necessary for outer segment disc membrane evagination or the fusion event that controls disc sealing. Rather, they are necessary for the higher-order organization of the outer segment. Prom1 may align and reinforce interactions between nascent disc leading edges, a function more critical in cones for structural support. Cdhr1 may secure discs in a horizontal orientation prior to fusion and regulate cone lamellae size.This article has an associated First Person interview with the first author of the paper.

Prominin-1 and Photoreceptor Cadherin Localization in Xenopus laevis: Protein-Protein Relationships and Function.

Retinal degenerative diseases are genetically diverse and rare inherited disorders that cause the death of rod and cone photoreceptors, resulting in progressive vision loss and blindness. This review will focus on two retinal degeneration-causing genes: prominin-1 (prom1) and photoreceptor cadherin (prCAD). We will discuss protein localization, potential roles in photoreceptor outer segment disc morphogenesis, and areas for future investigation.

Hypersensitivity reactions associated with L-asparaginase administration in 142 dogs and 68 cats with lymphoid malignancies: 2007-2012.

Clinically significant hypersensitivity reactions (HSRs) to the chemotherapy drug L-asparaginase are reported in humans and dogs, but frequency in small animals is not well-defined. This study retrospectively evaluated the frequency of HSR to L-asparaginase given by IM injection to dogs and cats with lymphoid malignancies. The medical records of all dogs and cats treated with at least 1 dose of L-asparaginase chemotherapy over a 5-year period were reviewed. A total of 370 doses of L-asparaginase were administered to the dogs, with 88 of 142 dogs receiving multiple doses, and 6 dogs experiencing an HSR. A total of 197 doses were administered to the cats, with 33 of 68 cats receiving multiple doses, and no cats experiencing an HSR. Hypersensitivity reactions were documented in 4.2% of dogs, and in association with 1.6% of L-asparaginase doses administered. These results show that HSRs occur uncommonly among dogs and cats, even with repeated dosing.

Réactions d'hypersensibilité associées à l'administration de L-asparaginase chez 142 chiens et 68 chats atteints de tumeurs malignes lymphoïdes: 2007­2012. Des réactions d'hypersensibilité cliniquement significatives (HCS) au médicament de chimiothérapie L-asparaginase sont signalées chez les humains et les chiens, mais leur fréquence chez les petits animaux n'est pas bien définie. Cette étude a évalué rétrospectivement la fréquence des HCS au médicament L-asparaginase administré par injection IM aux chiens et aux chats atteints de tumeurs malignes lymphoïdes. On a examiné les dossiers médicaux de tous les chiens et chats traités avec au moins une dose de chimiothérapie au médicament L-asparaginase pendant une période de 5 ans. Un total de 370 doses de L-asparaginase a été administré aux chiens, 88 des 142 chiens ont reçu des doses multiples et 6 chiens ont manifesté des HCS. Un total de 197 doses ont été administrées aux chats, 33 des 68 chats ont reçu des doses multiples et aucun chat n'a manifesté des HCS. Les HCS ont été documentées chez 4,2 % des chiens et en association avec 1,6 % des doses de L-asparaginase administrées. Ces résultats indiquent que les HCS se produisent rarement chez les chiens et les chats, même avec des doses répétées.(Traduit par Isabelle Vallières).

Prominin-1 null Xenopus laevis develop subretinal drusenoid-like deposits, cone-rod dystrophy, and RPE atrophy.

Mutations in the PROMININ-1 (PROM1) gene are associated with inherited, non-syndromic vision loss. Here, we used CRISPR/Cas9 to induce truncating prom1-null mutations in Xenopus laevis to create a disease model. We then tracked progression of retinal degeneration in these animals from the ages of 6 weeks to 3 years old. We found that retinal degeneration caused by prom1-null is age-dependent and likely involves death or damage to the retinal pigment epithelium (RPE) that precedes photoreceptor degeneration. As prom1-null frogs age, they develop large cellular debris deposits in the subretinal space and outer segment layer which resemble subretinal drusenoid deposits (SDD) in their location, histology, and representation in color fundus photography and optical coherence tomography (OCT). In older frogs, these SDD-like deposits accumulate in size and number, and they are present before retinal degeneration occurs. Evidence for an RPE origin of these deposits includes infiltration of pigment granules into the deposits, thinning of RPE as measured by OCT, and RPE disorganization as measured by histology and OCT. The appearance and accumulation of SDD-like deposits and RPE thinning and disorganization in our animal model suggests an underlying disease mechanism for prom1-null mediated blindness of death and dysfunction of the RPE preceding photoreceptor degeneration, instead of direct effects upon photoreceptor outer segment morphogenesis, as was previously hypothesized.

Literature review details and supports the application of platelet-rich plasma products in canine medicine, particularly as an orthobiologic agent for osteoarthritis.

Platelet-rich plasma (PRP) and other platelet-derived products represent a subset of regenerative medicine and have been researched in the veterinary community for the treatment of osteoarthritis, soft tissue wounds, tendinopathies, periodontitis, and fracture repairs. PRP is simple to produce, relatively affordable, safe, and can be delivered on site, making it an appealing therapeutic agent in veterinary medicine. As an orthobiologic for the treatment of osteoarthritis, it is one of few interventions with clinical study support that possess anabolic potential. Platelet product variability is wide ranging and often described in terms of cellular content or platelet enrichment. Growth factors associated with platelet activation and subsequent degranulation may mediate inflammation, modulate cellular immune response, and promote tissue repair. Product composition, dosage, and application likely influence treatment outcomes depending on the classification of the disease targeted. Sufficient canine data regarding the formulation and clinical application of canine PRP exist to warrant review. The aim of this narrative is to provide scientific background and clinical insight for veterinarians regarding platelet product content/formulation, mechanisms of action, considerations for use, and clinical application in dogs.

Alpha2 -adrenoceptor agonists inhibit form-deprivation myopia in the chick.

BACKGROUND: The putative myopia-controlling receptor is thought to be muscarinic acetylcholine receptor subtype M4 , because mamba toxin-3 can inhibit form-deprivation myopia in chicks at a far lower concentration than atropine. However, mamba toxin-3 is equally potent at the human α1A -, α1D -, and α2A -adrenoceptors. To test the hypothesis that α-adrenoceptors might be involved in regulation of eye growth, the treatment effects of α2 -adrenoceptor agonists brimonidine, clonidine, and guanfacine, and antagonist yohimbine, on form-deprivation myopia in the chick were measured. METHODS: Right eyes of White Leghorn chicks were goggled with diffusers to induce form-deprivation myopia; left eyes were left open as controls. Goggled eyes were injected intravitreally with 20 µL of vehicle, or 2, 20, or 200 nmol of brimonidine, clonidine, guanfacine, or yohimbine, 24, 72, and 120 hours after goggle application. Alternatively, myopia was inhibited physiologically by goggle removal for two hours, and the α2 -adrenoceptor antagonist, yohimbine, was injected to test whether it could block this type of myopia inhibition. One day after the last injection, refractive error and axial length were measured. RESULTS: Brimonidine (20 and 200 nmol) and clonidine (200 nmol) effectively inhibited experimentally induced increases in negative refractive error and axial elongation. All doses of guanfacine significantly inhibited induced negative refractive error, but only 20 and 200 nmol significantly inhibited axial elongation. Yohimbine had no effect on form-deprivation myopia, but 200 nmol reduced the myopia-inhibiting effect of goggle removal. CONCLUSION: High concentrations of α2 -adrenoceptor agonists, similar to those required by atropine, inhibited chick form-deprivation myopia; antagonism by yohimbine had no effect. High-concentration yohimbine partially interfered with emmetropisation in form-deprived chicks experiencing normal vision for two hours per day. These data support the hypothesis that treatment with high concentrations of adrenergic drugs can affect experimentally induced myopia and normal visual processes.

Rate of return to agility competition for dogs with cranial cruciate ligament tears treated with tibial plateau leveling osteotomy.

OBJECTIVE To determine rate of and factors associated with return to agility competition for dogs with cranial cruciate ligament (CrCL) rupture treated with tibial plateau leveling osteotomy (TPLO). DESIGN Retrospective case series with nested case-control study. ANIMALS 31 dogs involved in agility competition with CrCL tears treated by TPLO at a private veterinary clinic from 2007 through 2013. PROCEDURES Medical records were reviewed to collect information on dog signalment, lesion characteristics, and surgical data. Owners completed a survey regarding whether and when their dog returned to agility competition after TPLO and, if so, how the dog performed. Performance data before and after TPLO were compared. RESULTS 20 of 31 (65%) dogs returned to agility competition after TPLO, 16 (80%) of which returned within 9 months after TPLO. The mean convalescent period for returning dogs was 7.5 months (range, 3 to 12 months). No dog that returned to competition sustained an injury to the affected limb during the follow-up period. No significant difference was identified between dogs that returned or did not return to agility competition regarding severity of osteoarthritis or proportions with meniscal injury or partial (vs complete) CrCL tears. CONCLUSIONS AND CLINICAL RELEVANCE These data suggested that the prognosis for returning to agility competition was good for dogs undergoing TPLO. None of the evaluated lesion characteristics were associated with return to competition. Rate of return to competition and duration of the convalescent period may be useful outcome variables for future investigations involving orthopedic procedures in dogs.

Myopia-Inhibiting Concentrations of Muscarinic Receptor Antagonists Block Activation of Alpha2A-Adrenoceptors In Vitro.

Purpose: Myopia is a refractive disorder that degrades vision. It can be treated with atropine, a muscarinic acetylcholine receptor (mAChR) antagonist, but the mechanism is unknown. Atropine may block α-adrenoceptors at concentrations ≥0.1 mM, and another potent myopia-inhibiting ligand, mamba toxin-3 (MT3), binds equally well to human mAChR M4 and α1A- and α2A-adrenoceptors. We hypothesized that mAChR antagonists could inhibit myopia via α2A-adrenoceptors, rather than mAChR M4. Methods: Human mAChR M4 (M4), chicken mAChR M4 (cM4), or human α2A-adrenergic receptor (hADRA2A) clones were cotransfected with CRE/promoter-luciferase (CRE-Luc; agonist-induced luminescence) and Renilla luciferase (RLuc; normalizing control) into human cells. Inhibition of normalized agonist-induced luminescence by antagonists (ATR: atropine; MT3; HIM: himbacine; PRZ: pirenzepine; TRP: tropicamide; OXY: oxyphenonium; QNB: 3-quinuclidinyl benzilate; DIC: dicyclomine; MEP: mepenzolate) was measured using the Dual-Glo Luciferase Assay System. Results: Relative inhibitory potencies of mAChR antagonists at mAChR M4/cM4, from most to least potent, were QNB > OXY ≥ ATR > MEP > HIM > DIC > PRZ > TRP. MT3 was 56× less potent at cM4 than at M4. Relative potencies of mAChR antagonists at hADRA2A, from most to least potent, were MT3 > HIM > ATR > OXY > PRZ > TRP > QNB > MEP; DIC did not antagonize. Conclusions: Muscarinic antagonists block hADRA2A signaling at concentrations comparable to those used to inhibit chick myopia (≥0.1 mM) in vivo. Relative potencies at hADRA2A, but not M4/cM4, correlate with reported abilities to inhibit chick form-deprivation myopia. mAChR antagonists might inhibit myopia via α2-adrenoceptors, instead of through the mAChR M4/cM4 receptor subtype.

Nitric Oxide (NO) Mediates the Inhibition of Form-Deprivation Myopia by Atropine in Chicks.

Myopia is the most common childhood refractive disorder. Atropine inhibits myopia progression, but its mechanism is unknown. Here, we show that myopia-prevention by atropine requires production of nitric oxide (NO). Form-deprivation myopia (FDM) was induced in week-old chicks by diffusers over the right eye (OD); the left eye (OS) remained ungoggled. On post-goggling days 1, 3, and 5, OD received intravitreally 20 µL of phosphate-buffered saline (vehicle), or vehicle plus: NO source: L-arginine (L-Arg, 60-6,000 nmol) or sodium nitroprusside (SNP, 10-1,000 nmol); atropine (240 nmol); NO inhibitors: L-NIO or L-NMMA (6 nmol); negative controls: D-Arg (10 µmol) or D-NMMA (6 nmol); or atropine plus L-NIO, L-NMMA, or D-NMMA; OS received vehicle. On day 6 post-goggling, refractive error, axial length, equatorial diameter, and wet weight were measured. Vehicle-injected goggled eyes developed significant FDM. This was inhibited by L-Arg (ED50 = 400 nmol) or SNP (ED50 = 20 nmol), but not D-Arg. Higher-dose SNP, but not L-Arg, was toxic to retina/RPE. Atropine inhibited FDM as expected; adding NOS-inhibitors (L-NIO, L-NMMA) to atropine inhibited this effect dose-dependently, but adding D-NMMA did not. Equatorial diameter, wet weight, and metrics of control eyes were not affected by any treatment. In summary, intraocular NO inhibits myopia dose-dependently and is obligatory for inhibition of myopia by atropine.

Partial Cranial Cruciate Ligament Tears Treated with Stem Cell and Platelet-Rich Plasma Combination Therapy in 36 Dogs: A Retrospective Study.

OBJECTIVE: To evaluate outcomes in 36 dogs with a partial cranial cruciate ligament (CCL) tear treated with autologous bone marrow aspirate concentrate (BMAC) or adipose-derived progenitor cells (ADPC) with platelet-rich plasma (PRP) combination. MATERIALS AND METHODS: Medical records of client-owned dogs diagnosed with an early partial (≤50%) tear of the craniomedial band of the CCL that was treated with BMAC-PRP or ADPC-PRP were reviewed from 2010 to 2015. Signalment, medical history, physical and orthopedic examination, objective temporospatial gait analyses, radiographs, day 0 and day 90 diagnostic arthroscopy findings, treatment, and outcome were among the data collected. A functional owner questionnaire, including the validated Helsinki chronic pain index (HCPI), was sent to owners whose dog was known to not have had a tibial plateau leveling osteotomy (TPLO). Statistical analysis was performed on data, where significance was established at p < 0.05. RESULTS: Stifle arthroscopy findings at 90 days posttreatment were available on 13 of the 36 dogs. In nine dogs, a fully intact CCL with marked neovascularization and a normal fiber pattern was found with all previous regions of disruption healed. One dog revealed significant improvement and received an additional injection. The remaining three dogs had a >50% CCL tear, and a TPLO was performed. Four additional dogs were known to have had a TPLO performed elsewhere. Baseline and day 90 posttreatment objective gait analyses were available on 11 of the 36 dogs. A significant difference was found between the treated limb total pressure index percent (TPI%) at day 0 and day 90 (p = 0.0124), and between the treated limb and contralateral limb TPI% at day 0 (p = 0.0003). No significant difference was found between the treated limb and contralateral limb TPI% at day 90 (p = 0.7466). Twelve questionnaires were returned, of which eight were performance/sporting dogs. Seven of the eight had returned to sport; the remaining dog had just begun a return to sport conditioning program 6 months posttreatment. All 12 respondents believed that their dog had an excellent or very good quality of life and rated their dog's procedural outcome as excellent or good. CONCLUSION: The use of BMAC-PRP and ADPC-PRP shows promise for the treatment of early partial CCL tears in dogs. Further studies are needed and should be randomized, blinded, and controlled.

Adhesive Capsulitis in Eight Dogs: Diagnosis and Management.

OBJECTIVE: To describe clinical and diagnostic findings as well as management of adhesive capsulitis in dogs. BACKGROUND: Adhesive capsulitis, also known as frozen shoulder, is a syndrome defined by loss of range of motion of the shoulder and may be the end-stage manifestation of several primary conditions. EVIDENTIARY VALUE: This is a case series report of eight dogs with chronic forelimb lameness diagnosed with adhesive capsulitis. METHODS: Medical records (June 1, 2010-September 1, 2015) including, physical examination findings, radiographic findings, magnetic resonance imaging (MRI) findings, arthroscopy findings, and treatment plans were reviewed. RESULTS: All dogs presented with a chronic, grade III-VI/VI forelimb lameness. On orthopedic examination, all dogs had moderate to significant discomfort on shoulder extension and flexion and severe restriction of range of motion. Six of the eight dogs had evidence of bone remodeling and sclerosis in the affected shoulder on radiographs. Six of the dogs had an initial diagnostic ultrasound performed, which revealed evidence of fibrous scar tissue. Five dogs had MRI performed that revealed moderate shoulder effusion and enhancement of the synovial lining of the shoulder. Arthroscopy was performed in five of the eight patients. Three were noted to have significant contracture, adhesions, and fibrous scar tissue of the joint capsule. Severe inflammation was noted throughout the synovium of two patients. All eight patients tried conservative management consisting of oral medications and rehabilitation therapy. Five of the eight patients received extracorporeal shockwave therapy. Three patients received regenerative medicine treatment in the affected supraspinatus and shoulder. Regardless of the treatment elected, none of the dogs were reported to have significant improvement. CONCLUSION: Adhesive capsulitis is an uncommon cause of chronic forelimb lameness. Further investigation is needed to describe the etiology and pathogenesis of adhesive capsulitis in dogs to evaluate the effectiveness of both non-surgical and surgical treatment modalities, establish treatment protocols, and evaluate short- and long-term clinical outcome of patients. APPLICATION: Adhesive capsulitis should be considered in patients with chronic forelimb lameness and moderate to significant discomfort and restriction on shoulder range of motion.